Ankle braces are generally used to apply pressure to the ankle to prevent movement thereof after sustaining an injury. A constraint upon the application of such pressure is that it must generally restrict inversion and eversion (lateral) movement of the ankle while allowing the normal walking flexion of the ankle to occur.
In prior art attempts to construct an ankle brace which performs in accordance with the above constraint, inflatable air bladders have been used for developing the required pressure. For example, described in U.S. Pat. No. 3,811,434 (the '434 patent) is an inflatable splint having a flexible inflatable body portion to one side of which is joined a panel of flexible sheet material. The panel forms an open-ended sleeve with the body portion to admit a limb or the like and to enable the splint to be positioned. After the splint is properly positioned, the body portion is inflated. FIG. 7 of the '434 patent illustrates the use of the above-describe splint as an ankle brace.
A limitation and disadvantage of the inflatable spirnt described in the 434 patent is that when used on an ankle brace as shown therein inversion and eversion of the ankle is not adequately restrained since the inflatable body portion is designed to apply pressure against the shin and top of the foot thereby causing a tightening of the sheet material. At the ankle, the sheet material would only exhibit a minimal compressive force or pressure on the ankle due to the lateral tension between the body portion and sheet material. The further disadvantage and limitation of the above described splint is that it would resist normal walking flexion, which is desirable to promote healing, as the inflatable body portion would tend to straighten itself causing extension of the ankle. Also, the inflatable body portion would not be capable of being worn under a shoe, since the shoe would likely prevent proper inflation of the body portion under the shoe.
Another prior art ankle brace is described in U.S. Pat. No. 4,280,489 (the '489 patent). The brace of the '489 patent has a generally U-shaped stirrup having a base portion and a pair of opposed sidewall portions. An air inflatable liner is attached to the interior of each side wall and is dimensioned to extend coextensively therewith. The sidewall portions snugly fit about the lower leg above the ankle. Inflation of each liner applies pressure to the ankle.
A disadvantage and limitation of the device described in the '489 patent is that the use of air or any gaseous medium to provide the pressure on the ankle does not adequately prevent inversion or eversion of the ankle. For example, a sudden localized pressure applied to the air inflated liner is not resisted. The liner will be locally compressed causing the air to migrate to another portion of the liner to equalize the air pressure on the inner surface of the liner. Therefore, the air inflatable liner may not adequately restrain a sudden inversion or eversion of the ankle but may cause the stirrup to shift in position under such sudden and localized forces.
High viscosity gels are known to be highly resistive to sudden localized forces. These gels have found useful applications in ski boots. For example, see U.S. Pat. No. 3,237,319. Generally, a bladder is attached to an interior wall of the ski boot, the wall of the ski boot necessarily being extremely rigid The gel may be introduced into the bladder before or after the foot is placed in the boot. The gel, when the boot is tightened, will cause momentary discomfort but will gradually flow to conform to the shape of the ankle giving a high degree of comfort and support. Since the wall of the ski boot is rigid, the bladder will remain conformed to the ankle. During skiing, forces which may normally cause sudden inversion or eversion of the ankle are resisted because the high viscosity of the gel and its resistance to rapid deformation.
Although gel filled bladders are relatively advantageous in restraining inversion and eversion of the ankle when used within a ski boot, there are many problems and difficulties which arise when such bladders are to be substituted for the air filled liners of the above described ankle braces. Since it is highly desirable that such ankle braces be worn under clothing and especially shoes, the ankle brace must be relatively thin and flexible as opposed to the rigid wall of the ski boot. Since the high viscosity gel will gradually conform to the shape by which it is constrained, the gel bladder, if used in the prior art ankle braces will assume a shape that equalizes pressure the gel exerts across the inner surface of the bladder. For example, a shoe may cause the gel to evacuate partially from the bladder between the shoe and the ankle. Generally, the slow migration of the gel may cause the bladder to assume a shape which no longer supports the ankle against sudden inversion or eversion.
Attention is also directed to G. W. Johnson U.S. Pat. No. 4,628,945 in which an inflatable bladder is filled with foam and forms padding within a pair of rigid plastic members. In this regard, it may be noted general)y that braces of the type shown in the Johnson 945 and '489 patents, with stiff outer plastic members, are intended for use with incomplete or stable fractures, in some cases after partial mending, and for serious sprains, such as Grade III sprains. In addition, the engagement provided by the air bladder padding, even with a foam filler, is not as stable as might be desired, and is not compatible with hot and/or cold therapy.
J. W. Sconce U.S. Pat. No. 3,901,225 is also of interest in showing a rectangular or trapezoidal assembly forming a cast for immobilizing a fracture, using various hot or cold materials, with no mention of gel. Air inflation for immobilization and for forcing ice water or the like into contact with the fractured limb is provided.
The Spence U.S. Pat. No. 3,548,420 is also noted as disclosing simple gel pad structures and indicating the possibility of using gel pads with a "Milwaukee Brace", without disclosing any applicable structural arrangements.